Apparatus and methods for accessing a data network

ABSTRACT

A packet data network gateway, P-GW, is located in a second network for supporting control plane data in a wireless communications system that additionally comprises a first network having a first P-GW operably couplable to the P-GW, and a serving gateway, S-GW. The P-GW comprises a processor arranged to: monitor and build terminal device context information for a plurality of terminal devices being served with user plane data by the second network; and determine an operational status of at least one of: the backhaul link, first P-GW. In response to the processor determining that at least one of: the backhaul link, first P-GW, is unavailable, the processor is arranged to perform at least one of: terminate signalling between the first network and at least one of a mobility management entity, MME, the S-GW; defer signalling between the first network and at least one of the MME, the S-GW; perform at least some functionality of the first P-GW.

FIELD OF THE INVENTION

The field of the invention relates to methods and apparatus foraccessing data networks, for example packet data network gateways.

BACKGROUND OF THE INVENTION

A recent development in third generation (3G) wireless communications isthe long term evolution (LTE) cellular communication standard, sometimesreferred to as 4th generation (4G) systems. Both of these technologiesare compliant with third generation partnership project (3GPP™)standards. Irrespective of whether LTE spectral allocations use existingsecond generation (2G) or 3G allocations being re-farmed for fourthgeneration (4G) systems, or new spectral allocations for existing mobilecommunications, they will generally use paired spectrum for frequencydivision duplex (FDD) operation.

Referring to FIG. 1, an example of a simplified evolved packet system(EPS) 100 is illustrated comprising, part of an evolved packet core(EPC) network 101, access network 103 and user equipment (UE) domain105. In this case, EPC network 101 comprises the Internet 128, a packetdata network gateway (P-GW) 107, a serving gateway (S-GW) 111 and amobility management entity (MME) 113. The P-GW 107 is situated betweenthe Internet 128 and the S-GW 111, and may include responsibility for IPaddress allocation for UEs 115, as well as Quality of Service (QoS)enforcement and flow based charging according to rules of a policycontrol and charging rules function (not shown). The P-GW 107 isresponsible for filtering of downlink user Internet Protocol (IP)packets into different QoS-based bearers. The P-GW 107 also serves as amobility anchor for inter-working with non-3GPP technologies such asCDMA2000 and WiMAX™ networks. All IP packets are transferred from theP-GW 107 to the serving gateway (S-GW) 111 via an S5/S8 interface, whichserves as a local mobility anchor for data bearers when user equipment(UEs) 115 move between base stations/eNodeBs 117. The S-GW 111 alsoretains the information about the bearers when the UEs are in idle state(known as EPS Connection Management IDLE (ECM-IDLE)) and temporarilybuffers downlink data while the MME 113 initiates paging of the UEs 115to re-establish the bearers. In addition, the S-GW 111 performs someadministrative functions in the access network 103, such as collectinginformation for charging and legal interception. It also serves as amobility anchor for inter-working with other 3GPP technologies such asgeneral packet radio service (GPRS) and universal mobiletelecommunications service (UMTS). The S-GW 111 is coupled to the MME113 via an S11 interface.

Access network 103, defined by a number of inter-connected eNodeBs 117,is generally utilised when UEs 115 are in a network's coverage area 119,thereby allowing UEs 115 to communicate with each other solely via theaccess network 103. Generally, the access network 103 communicates withthe EPC network 101 via S1-U 121 and S1-MME 123 interfaces. eNodeBs 117are operable to communicate with each other within the access network103 via X2 interfaces 125. In this case, UEs 115 are operable tocommunicate with eNodeBs 117 via a Uu interface, otherwise known asradio interface 127. In this case, access network 103 is utilised whenUEs 115 are within the access network's 103 network coverage 119,allowing them to communicate with one another. Generally, the accessnetwork 103 facilitates communication by receiving control plane dataand user plane data from each eNodeB 117 and from UEs 115, andtransmitting this control plane data and user plane data to the othereNodeBs 117 within the access network 103. Different eNodeBs 117 withinthe access network 103 may utilise different receiving and transmittingfrequencies, for example if Frequency Division Duplexing (FDD) isutilised. Further, different eNodeBs 117 within the access network 103may utilise different waveforms, signal modulation and coding schemesbetween the different eNodeBs 117. Specifically, in a generic LTEsystem, referred to as E-UTRAN, the Uu radio interface 127 generallyutilises Orthogonal Frequency Division Multiple Access (OFDMA) in theDownlink and Single Carrier Frequency Division Multiple Access (SC-FDMA)in the Uplink. OFDMA distributes subcarriers to different users (UEs) atthe same time, allowing multiple users to be scheduled to receive datasimultaneously.

Generally, subcarriers are allocated in contiguous groups for simplicityand to reduce any overhead of indicating which subcarriers have beenallocated to each user. SC-FDMA is generally utilised in the Uplink caseas it has a lower peak-to-average power ratio compared to OFDMA, whichcan benefit mobile terminal devices in terms of transmit powerefficiency, for example. As discussed above, FDD may be utilisedresulting in differing transmit and receive carrier frequencies.Further, Time Division Duplexing (TDD) may be utilised, resulting inseparate outward and return signals.

A potential problem occurs when, for example, the P-GW 107 within theEPC network 101 fails. If this failure occurs, at least user plane datawill be affected, and it may not be possible to access the packet datanetwork 128 or route data to the UEs 115. Failure of the P-GW 107 mayprevent public safety systems from offering services to local users.Therefore, in some cases, it may be desirable for public safety systemsto be able to offer services to local users despite failures within theEPC network 101.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a packet data network gateway, P-GW,is located in a second network for supporting control plane data in awireless communications system that additionally comprises a firstnetwork having a first P-GW operably couplable to the P-GW, and aserving gateway, S-GW. The P-GW comprises a processor arranged to:monitor and build terminal device context information for a plurality ofterminal devices being served with user plane data by a backhaul link ofthe second network; and determine an operational status of at least oneof: the backhaul link, first P-GW. In response to the processordetermining that at least one of: the backhaul link, first P-GW, isunavailable, the processor is arranged to perform at least one of:terminate signalling between the first network and at least one of amobility management entity (MME), and/or the S-GW; defer signallingbetween the first network and at least one of the MME and/or the S-GW;perform at least some functionality of the first P-GW.

Optionally, the processor may be arranged to build terminal devicecontext information from signalling used to establish the single packetdata network connection.

Optionally, the processor may be operably coupled to a memory elementarranged to store the terminal device context information.

Optionally, the processor may be arranged to extract signallinginformation between the MME and/or SGW and the first P-GW and perform atleast one of adapting the extracted signalling information passedbetween the MME and/or SGW and the first P-GW and forward the signallinginformation to the first P-GW.

Optionally, the processor may be arranged to monitor and build terminaldevice context information for a plurality of terminal devices beingserved with user plane data by the second network.

Optionally, the processor may be further arranged to check a destinationaddress of received packets to determine whether the received packetsare destined for any of the plurality of terminal devices, and extractone or more properties of said received packets if they are destined forany of the terminal devices served with user plane data by the secondnetwork.

Optionally, the processor may further perform packet analysis orstatistical analysis on said received packets.

Optionally, the processor may further invoke a bearer mapping functionwithin the second network.

Optionally, the processor further may invoke a bearer mapping functionwithin the second network based on at least one from a group of: one ormore source IP address(es), one or more destination IP address(es), oneor more source port number(s), one or more destination port number(s),one or more protocol type packet properties, packet analysis on saidreceived packets.

Optionally, the processor may be further arranged to check a destinationaddress of received packets to determine whether the received packetsare destined for any of the terminal devices, and discard said receivedpackets if they are not destined for any of the terminal devices servedwith user plane data by the second network.

Optionally, the processor may be further arranged to check a destinationaddress of received packets to determine whether the received packetsare destined for a local packet data network, and discard said receivedpackets if they are not destined for the local packet data network.

Optionally, the processor may be arranged to perform at least somefunctionality of the first P-GW comprising the processor arranged toallocate an internet protocol address to the terminal device uponreceipt of a message from the terminal device indicating a requirementto attach or establish a new PDN connection.

According to a second aspect of the invention, a method of operation ofa (second) packet data network gateway (P-GW) is located in a secondnetwork for supporting control plane data in a wireless communicationssystem that additionally comprises a first network having a first packetdata network gateway (P-GW) operably couplable to the (second) P-GW; themethod comprising, at the (second) P-GW: monitoring and buildingterminal device context information for a plurality of terminal devicesbeing served with user plane data by a backhaul link of the secondnetwork; determining an operational status of at least one of: thebackhaul link, first P-GW, and in response to the processor determiningthat at least one of: the backhaul link, first P-GW, is unavailable,performing at least one of: terminating signalling between the firstnetwork and at least one of: a mobility management entity (MME), and/orSGW; deferring signalling between the first network and at least one ofthe MME and/or the SGW; performing at least some functionality of thefirst P-GW, is illustrated.

According to a third aspect of the invention, a non-transitory computerprogram product comprising executable program code for operation of a(second) packet data network gateway (P-GW) located in a second networkfor supporting control plane data in a wireless communications systemthat additionally comprises a first network having a first packet datanetwork gateway (P-GW), the executable program code operable for, whenexecuted at the (second) P-GW, performing the abovementioned method.

According to a fourth aspect of the invention, an integrated circuit issuitable for a (second) packet data network gateway, P-GW, located in a(second) network for supporting control plane data in a wirelesscommunications system that additionally comprises a (first) networkhaving a first P-GW operably couplable to the P-GW, and a servinggateway, S-GW. The integrated circuit comprises a processor arranged to:monitor and build terminal device context information for a plurality ofterminal devices being served with user plane data by a backhaul link ofthe second network; and determine an operational status of at least oneof: the backhaul link, first P-GW. In response to the processordetermining that at least one of: the backhaul link, first P-GW, isunavailable, the processor is arranged to perform at least one of:terminate signalling between the first network and at least one of amobility management entity (MME), and/or the S-GW; defer signallingbetween the first network and at least one of the MME and/or the S-GW;perform at least some functionality of the (first) P-GW.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details, aspects and embodiments of the invention will bedescribed, by way of example only, with reference to the drawings. Inthe drawings, like reference numbers are used to identify like orfunctionally similar elements. Elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.

FIG. 1 illustrates a simplified known example of an evolved packetsystem.

FIG. 2 illustrates a 3GPP™ LTE cellular communication system adapted inaccordance with some example embodiments of the present invention.

FIG. 3 illustrates an example block diagram of a simplified example of awireless communications system adapted in accordance with some exampleembodiments of the present invention.

FIG. 4 illustrates the access network part of FIG. 3 adapted inaccordance with some example embodiments of the present invention.

FIG. 5 illustrates a simplified example of switching operation at alocal P-GW adapted in accordance with some example embodiments of thepresent invention.

FIG. 6 illustrates a simplified example of a flow diagram of a downlinkoperation of a wireless communications system adapted in accordance withsome example embodiments of the invention.

FIG. 7 illustrates a simplified example of a flow diagram of an uplinkoperation of a wireless communications system adapted in accordance withsome example embodiments of the invention.

FIG. 8 illustrates a simplified example of a flow diagram of furtherdetails of FIG. 7 in accordance with some example embodiments of theinvention.

FIG. 9 illustrates a simplified example of a flow diagram of operationsof a wireless communications system adapted in accordance with someexample embodiments of the invention.

FIG. 10 illustrates a simplified example of a flow diagram of connectionmanagement operations for a wireless communications system adapted inaccordance with some example embodiments of the invention.

FIG. 11 illustrates a typical computing system that may be employed toimplement software controlled switching between a first mode ofoperation, where a backhaul link may be available, and a second mode ofoperation where a backhaul link may not be available, adapted inaccordance with some example embodiments of the invention.

DETAILED DESCRIPTION

Referring now to FIG. 2, a wireless communication system 200 is shown inoutline, in accordance with an example embodiment of the invention. Inthis example embodiment, the wireless communication system 200 iscompliant with, and contains network elements capable of operating over,a 3rd Generation Partnership Project (3GPP™) air-interface. Inparticular, the embodiment relates to a system's architecture for anEvolved-UMTS Terrestrial Radio Access Network (E-UTRAN) wirelesscommunication system specification for long term evolution (LTE), basedaround OFDMA (Orthogonal Frequency Division Multiple Access) in thedownlink (DL) and SC-FDMA (Single Carrier Frequency Division MultipleAccess) in the uplink (UL), as described in the 3GPP™ TS 36.xxx seriesof specifications. Within LTE, both time division duplex (TDD) andfrequency division duplex (FDD) modes are defined.

The wireless communication system 200 architecture comprises of radioaccess network (RAN) and core network (CN) elements 204, with the corenetwork elements 204 being coupled to external networks 202 (namedPacket Data Networks (PDNs)), such as the Internet or a corporatenetwork. The CN elements 204 comprise a packet data network gateway(P-GW) 207. In order to serve up local content, the P-GW 207 may becoupled to a content provider. The P-GW 207 may be further coupled to apolicy control and rules function entity (PCRF) 297.

The PCRF 297 may be operable to control policy control decision making,as well as for controlling the flow-based charging functionalities in apolicy control enforcement function PCEF (not shown) that may reside inthe P-GW 207. The PCRF 297 may further provide a quality of service(QoS) authorisation class identifier and bit rate information thatdictates how a certain data flow will be treated in the PCEF, andensures that this is in accordance with a UE's 225 subscription profile.

A home subscriber server (HSS) database 230 may store UE subscriptiondata such as QoS profiles and any access restrictions for roaming. TheHSS database 230 may also store information relating to the P-GW 207 towhich a UE 225 can connect. For example, this data may be in the form ofan access point name (APN) or a packet data network (PDN) address. Inaddition, the HSS database 230 may hold dynamic information relating tothe identity of a mobility management entity (MME) 208 to which a UE 225is currently connected or registered.

The MME 208 may be further operable to control protocols running betweenthe user equipment (UE) 225 and the CN elements 204, which are commonlyknown as Non-Access Stratum (NAS) protocols. The MME 208 may support atleast the following functions that can be classified as: functionsrelating to bearer management (which may include the establishment,maintenance and release of bearers), functions relating to connectionmanagement (which may include the establishment of the connection andsecurity between the network and the UE 225) and functions relating tointer-working with other networks (which may include the handover ofvoice calls to legacy networks). The MME 208 may be further coupled toan evolved serving mobile location center (E-SMLC) 298 and a gatewaymobile location center (GMLC) 299.

The E-SMLC 298 may be operable to manage the overall coordination andscheduling of resources required to find the location of the UE that isattached to the RAN, in this example embodiment the E-UTRAN. The GMLC299 may contain functionalities required to support location services(LCS). After performing an authorisation, it may send positioningrequests to the MME 208 and receive final location estimates.

The P-GW 207 is operable to determine IP address allocation for a UE225, as well as QoS enforcement and flow-based charging according torules received from the PCRF 297. The P-GW 207 is further operable tocontrol the filtering of downlink user IP packets into differentQoS-based bearers (not shown). The P-GW 207 may also serve as a mobilityanchor for inter-working with non-3GPP™ technologies such as CDMA2000and WiMAX™ networks.

As illustrated, the CN 204 is operably connected to two eNodeBs 210,with their respective coverage zones or cells 285, 290 and a pluralityof UEs 225 receiving transmissions from the CN 204 via the eNodeBs 210.In accordance with example embodiments of the present invention, atleast one P-GW (203) (amongst other elements) has been adapted tosupport the concepts hereinafter described.

The main component of the RAN is an eNodeB (an evolved NodeB) 210, whichperforms many standard base station functions and is connected to the CN204 via an S5/S8 interface and to the UEs 225 via a Uu interface. Awireless communication system will typically have a large number of suchinfrastructure elements where, for clarity purposes, only a limitednumber are shown in FIG. 2. The eNodeBs 210 control and manage the radioresource related functions for a plurality of wireless subscribercommunication units/terminals (or user equipment (UE) 225 in 3GPP™nomenclature). Each of the UEs 225 comprise a transceiver unit 227operably coupled to signal processing logic (with one UE illustrated insuch detail for clarity purposes only). The system comprises many otherUEs 225 and eNodeBs 210, which for clarity purposes are not shown.

In the evolved packet system 100 of FIG. 1, one P-GW 107 is allocatedper external packet data network (PDN) 128. With respect to transferringuser plane data, if this P-GW 107, which may be denoted as a first P-GW,becomes unavailable, it may not be possible to access the PDN or toroute data from or to UEs 115.

Thus, in accordance with some examples of FIG. 2, a further local EPC201 may be implemented within the wireless communications system 200,which may have some or all of the functionality of the EPC 204. Inexamples of the invention, the term ‘local’ may be interchanged with theterm ‘proxy’.

In some examples, the local EPC 201 may be situated in close proximityto the RAN domain. In other examples, the local EPC 201 may be situatedclose to an edge of the network domain, or co-located within one or moreeNodeBs 210. In yet more examples, the local EPC 201 may be located justoutside of the RAN domain.

In some examples, the local EPC 201 may comprise a local P-GW (203),which may, in some examples, function as a proxy P-GW, and may bedenoted as a second P-GW or a P-GW located in a second network. Thus, ifcommunications link 205 between P-GW 207 and local P-GW 203 is active,which may be a GRE or GTP tunnel, then a backhaul link is available.

In the context of this invention, a backhaul link may be defined as abackhaul portion of the network, which may comprise intermediate linksbetween the core network elements 204 and components of the RAN.

In this case, the local P-GW 203 may be operable to build up localcontext information by intercepting signalling information andforwarding or converting and forwarding (e.g. when GTP and PMIP basedinterfaces may be terminated at the local P-GW 203 to the P-GW 207 and aserving gateway, for example an S-GW 206 respectively) the interceptedsignalling information to the P-GW 207. If this backhaul link becomesunavailable, i.e. the P-GW 207 is no longer available or not functioningcorrectly, in one example embodiment the local P-GW 203 may take overand replace the P-GW 207 for at least some functionality, for example byterminating any new session management signalling, and deferringsignalling to the P-GW 207.

In this example embodiment, the S-GW 206 is located within the local EPC201, and may be operably coupled to MME 208 via an S11 interface andoperably coupled to the local P-GW 203. Further, the MME 208 may beoperably coupled to the local EPC 201 via an S1-MME interface. TheGateway 206 predominantly acts as a mobility anchor point and is capableof providing internet protocol (IP) distribution of user plane data toeNodeBs 210. The Gateway 206 may receive content via the P-GW 207, fromone or more content providers 209 or via the external PDN 202. As theGateway 206 comprises an S-GW, the eNodeBs 210 are connected to the S-GW206 and the MME 208 directly. In this case, all UE packets may betransferred through the S-GW 206, which may serve as a local mobilityanchor for the data bearers when a UE 225 moves between eNodeBs 210. TheS-GW 206 may also be capable of retaining information about the bearerswhen the UE 225 is in an idle state (known as EPS connection managementIDLE), and temporarily buffers downlink data while the MME 208 initiatespaging of the UE 225 to re-establish the bearers. In addition, the S-GW206 may perform some administrative functions in the visited network,such as collecting information for charging (i.e. the volume of datasent or received from the UE 225). The S-GW 206 may further serve as amobility anchor for inter-working with other 3GPP™ technologies such asGPRS™ and UMTS™.

If the backhaul subsequently becomes available, thereby allowing accessto P-GW 207 again, the local EPC 201 may trigger the deferred signallingand the local P-GW 203 may return to a ‘proxy’ mode of operation.

In the case of local EPC 201, processes may have to be put in place toallow management of user plane flows/bearers and switching between localEPC 201 and EPC 204 if, for example, part or all of EPC 204 becomesunavailable.

In some example embodiments, the S-GW 206 may be controlled via the MME208 or a local MME 211, which may also be situated within the local EPC201.

Referring to FIG. 3, a simplified wireless communications system 300 isillustrated in outline, in accordance with an example embodiment of theinvention. In this example, wireless communications system 300 maycomprise a PDN 302, an EPC 304 comprising at least a first P-GW, forexample main P-GW 306 and a first MME, for example main MME 307, and anaccess network 316, for example a E-UTRAN 308. Access network 316 maycomprise a plurality of eNodeBs 310, a second P-GW, for example localP-GW 312, an S-GW 314 and a second MME, for example local MME 315.Access network 316 may also include a local PDN 318.

UEs 320 may be operable to receive and transmit 321 via eNodeBs 310 andreceive user plane data 324, which may have originated from main P-GW306.

In this example, a backhaul link, represented by tunnel 322, may beavailable and, therefore, main P-GW 306 may be operational (this casemay be referred to as a ‘mode A’ of operation). Therefore, user planedata 324 may be transmitted by PDN 302 on an SGi 1 interface via themain P-GW 306 to the local P-GW 312 via tunnel 322, which may be a GREor GTP tunnel using an SGi 2 interface. User plane data 324 may then betransmitted to the local S-GW 314 on an S5 interface before beingtransmitted to UEs 320 via eNodeBs 310. In some examples, the IPaddress(es) for UEs 320 may be allocated by the main P-GW 306 or by thePDN 302. The local S-GW 314 may establish S5 bearers with the local P-GW312, and the local P-GW 312 may tunnel IP packets to the main P-GW 306via tunnel 322. In this case, QoS may be maintained as it is a managednetwork. Further, in some examples, main MME 307 may allocate the localS-GW 314 and the main P-GW 306, whereas the local MME 315 may allocatethe local P-GW 312 once the main MME 307 has allocated the main P-GW306. In this ‘mode A’ operating state, the local P-GW 312 may beoperable to forward user plane traffic to and from the main P-GW 306. Inthis case, the local P-GW 312 may perform data forwarding based ontunnel information stored in the UE context, or configured in mappingtables. For example, data transported over a particular GTP tunnel 322may be passed (de-capsulated/encapsulated) onto another tunnel (eitherGTP or GRE respectively, for GTP and MIP/PMIP operations). In someexamples, this operation may be applied in the reverse direction. Insome other examples, tunnel 322 may represent a plurality of tunnels.

In another example, for example a downlink scenario, the local P-GW 312may check internal queue(s) for each GTP tunnel/GRE tunnel coming fromthe main P-GW 306 and determine whether a new data packet is available.If the local P-GW 312 determines that there is not a new data packetavailable, it may continue to monitor the main P-GW 306. Otherwise, ifthe local P-GW 312 detects a new data packet, it may be operable todetermine the bearer/tunnel for which the new data packet was receivedin order to determine a corresponding destination tunnel/bearer (using aone-to-one mapping) and forward the new data packet over the determinedbearer/tunnel to the destination UE 320.

In some examples, local PDN 318 and PDN 302 may be identifiable by aunique access point name (APN). The local P-GW 312 may be operable, insome examples, to route data between UEs 320 and PDN 302 and local PDN318. In some examples, the local P-GW 312 may function as the main P-GW306 if backhaul link 322 is not available, Further, local P-GW 312 mayfunction as a proxy device if the backhaul link 322 is available,Therefore, local P-GW 312 may have dual functionality,

Referring now to FIG. 4, the example of the access network and UE part370 of FIG. 3 is illustrated, wherein connection to the main P-GW 306has been lost. Therefore, in this example, there may be no backhaullink, tunnel 322, between the main P-GW 306 and the local P-GW 412 (thiscase may be referred to as a ‘mode B’ of operation). In this example,the local P-GW 412 may monitor the main P-GW's 306 availability byutilising standard monitoring methods such as GTP-U or GRE linksupervision procedures. If a network outage is detected, i.e. there isno longer a backhaul link, for example tunnel 322, between main P-GW 306and local P-GW 412, the local P-GW 412 may switch to its ‘mode B’operating state. As a result, the local P-GW 412 may forward user planetraffic to local UEs 420 if the destination IP address is known, oralternatively discard the user plane traffic if the destination IPaddress is not known. In some cases, the local P-GW 412 may determinedestination IP addresses during its ‘mode A’ operating state.

In some further examples, it is envisaged that it may not be the localP-GW 412 that is operable to terminate and forward user plane data 424.For example, it may be that the S-GW 414 or the eNodeBs 410 may beoperable to loop data to UEs 420. However, the closer to the edge of thenetwork 416, the lower the probability that UEs 420, for which datapackets may be destined, will be known to other local entities withinaccess network 416. Therefore, in some examples, a hierarchicalstructure may be utilised, whereby each node 412, 414, 410 may checkwhether the UEs 420 for which data packets are destined are known, andact as above if one of the nodes in the hierarchical structure knows thedestination of the data packets.

Therefore, in some examples, an eNodeB 410 may receive information fromUE 420, and determine whether it knows the destination address of the UEinformation. If the eNodeB does know the destination address, it mayforward the information onto its destination. Otherwise, the eNodeB maypass the information onto S-GW 414. The S-GW 414 may perform a similaroperation to the eNodeB 410, and determine whether it knows thedestination address of the forwarded information from the eNodeB 410. Ifthe information reaches the local P-GW 412, and the local P-GW 412 doesnot know the destination address the local P-GW 412 may discard theinformation. In this way, a ‘packet lookup’ function is applied throughelements of the network.

Referring to FIG. 5, an example of a switching operation at a localP-GW, for example local P-GW 412 from FIG. 4, is illustrated inaccordance with an example of the invention. In this example, local P-GW412 may determine in detection module 501 if a main P-GW, for examplemain P-GW 306, is available. In this example, detection module 501 maybe, or incorporate, at least one processor, which may be operablycoupled to a backhaul link, for example at least one tunnel 322. Thedetection module/processor 501 may determine via link 502 if main P-GW306, for example, is available or not on the at least one tunnel 322.Further, detection module/processor 501 may be operable to store, in amemory 503, internal context information of registered UEs and their IPaddresses, obtained from interrogating the at least one tunnel 322 vialink 502. The detection module/processor 501 may be further operable tocontrol, via link 504, at least one switching module 515, which isoperable to transition between different modes of operation. If it isdetermined that the main P-GW 306 is available, the local P-GW 412 maybe in, or transition to, a ‘Mode A’ of operation, and receive 514 userplane data from a backhaul link, for example at least one tunnel 322,and relay 516 this information onto relevant bearers/UEs 420. In someexamples, during this mode of operation, the local P-GW 412 may, whileforwarding messages, analyse content of the forwarded messages andupdate local UE context information based on the information gathered.

If, however, it is detected 501 that the main P-GW 306 is not available,the local P-GW 412 may switch the at least one switching module 515 to a‘Mode B’ of operation, and forward 518 user plane data to relevantbearers/UEs 420. In this case, the forwarding 518 of user plane data maybe based on internal context information of the registered UEs 420 andtheir IP addresses. In some examples, the internal context informationmay have been determined during the ‘Mode A’ operating state when thelocal P-GW 412 may have analysed content of any forwarded messages. Itshould be noted that there is no IP routing for UE's U-Plane data withinthe local P-GW 412 as all data is carried over tunnels. However, ifcommunication with one or more local PDN 418 is required, IP routingwould be utilised. If the local P-GW 412 is not aware of the destinationof the user plane data, it may discard 520 the user plane data.

In some examples, it may be required to re-allocate local S-GW 414 (notshown). This may be, for example, if UEs 420 move out of the currentservice area serviced by local S-GW 414. The re-allocation of the localS-GW 414 may be performed by main MME 307 (not shown) or local MME 415(not shown) dependent, say, on operational circumstances. In aparticular example, the main MME 307 may be responsible forre-allocating the local S-GW 414 if there is a link between the mainP-GW 306 and the local P-GW 412. Otherwise, the local MME 412 may beresponsible for re-allocating the local S-GW 414 if the main P-GW 306 isunavailable, as in this case there may be no link between the main MME307 and the access network 316. In some cases, when re-allocating thelocal S-GW 414, it may be necessary for the main MME 307 or the localMME 415 to update binding information and local context information atthe local P-GW 412.

In some examples, the local P-GW 412 may be re-allocated as opposed tothe main P-GW 307, which may have been selected at the time a PDN, forexample PDN 302, (not shown) connection was established. This may be,for example, due to the local P-GW 412 being deployed in a geographicalregion serving local UEs 420, and its allocation may become sub optimalin relation to future geographical locations of the UEs 420.

Referring to FIG. 6, a flow diagram illustrating a downlink operation600 of a wireless communications system, for example the wirelesscommunications system illustrated in FIG. 3, is shown in accordance withan example embodiment of the invention.

At 602, downlink data, may be received at a local P-GW, for examplelocal P-GW 312, via a backhaul link, for example one or more tunnel(s)322. At 604, local P-GW 312 may check internal queue(s) for each GTPtunnel/GRE tunnel(s) 322 coming from a main P-GW, for example main P-GW306, and determine whether a new data packet(s) is available, forexample a user plane data packet. If, at 606, the local P-GW 312determines that a new data packet is not available, it may loop back to604. Otherwise, if it determines that a new data packet is available, itmay transition to 608 and detect the relevant bearer(s)/tunnel(s) forthe received data packet(s), and find corresponding destinationtunnel(s)/bearer(s) (one-to-one mapping). At 610, the local P-GW 312may, once destination tunnel(s)/bearer(s) have been located, forward thedata packet(s) over the detected bearer(s)/tunnel(s) to a destinationUE(s) before subsequently returning to 604.

This example may only be applicable where there is a backhaul linkavailable 322, for example where there is a connection between a mainP-GW 306 and local P-GW 312, as otherwise there would be no downlinkpackets to be received from the main P-GW 306.

Referring now to FIG. 7, a flow diagram illustrating an uplink operation700 of a wireless communications system, for example the wirelesscommunication system illustrated in FIGS. 3 and 4, is shown inaccordance with an example embodiment of the invention.

At 702, uplink packets, for example user plane data packets, receivedfrom UE(s), may be transmitted from local P-GW, for example local P-GW312/412, via a backhaul link, for example one or more tunnel(s) 322. At704, the local P-GW 312/412 may check internal queue(s) for each GTPtunnel(s)/GRE tunnel(s) coming from an S-GW, for example local S-GW314/414, and determine 706 whether a new uplink packet(s) is available.

If the local P-GW 312/412 determines at 706 that a new uplink packet(s)is not available, it may return to 704. Otherwise, if it determines at706 that a new uplink packet(s) is available, it may determine at 708whether a main P-GW, for example P-GW 306, is available. If local P-GW312/412 determines that main P-GW 306 is available, for example there isa backhaul link in place, then it may, at 710, re-encapsulate/forwardthe received uplink packet(s) onto a tunnel, for example one or moretunnels 322, established by main P-GW 306 (one-to-one mapping). If,however, local P-GW 312/412 determines that main P-GW is not availableat 708, for example there is no longer a backhaul link in place, then itmay, at 712, switch to an alternative mode of operation and checkwhether the uplink packet(s)′ destination IP address belongs to any UEcurrently served by it. In some examples, the local P-GW 314/414 mayanalyse data during 710 and update its records to enable it to determineIP addresses belonging to UEs served by it.

If local P-GW 314/414 determines that the destination IP address ofuplink packet(s) does not belong to any UE(s) it is currently serving,it may discard 714, in some examples silently discard, the uplinkpacket(s) and continue monitoring the system at 704. If, however, thelocal P-GW 314/414 determines that the destination IP address of uplinkpacket(s) does belong to any UE(s) it is currently serving, it mayperform a packet classification and mapping procedure 716 beforerouting/re-encapsulating/forwarding 718 uplink packet(s) over previouslymapped bearers to a destination UE(s), and subsequently returning to704.

Referring to FIG. 8, a further flow diagram illustrating aspects of FIG.7 in further detail is shown in accordance with an example embodiment ofthe invention. In this case, FIG. 8 may relate to the packetclassification and mapping stage 716 of FIG. 7. Initially, at 802,uplink packet classification may commence and, at 804, a local P-GW, forexample P-GW 314/414, may obtain an IP address of a source UE that maybe based on bearer identification information from previously receiveduplink packet data. In some cases, packet screening may be required. At806, local P-GW 314/414 may extract destination IP address(es) fromtunnel(s), for example from a payload of a GTP packet (a bearer) or GREtunnel(s), and, at 808, check a database, which may be an internaldatabase, in order to determine whether or not context informationexists for the extracted destination IP address(es). If, at 810, thelocal P-GW 314/414 determines that context information does exist forthe one or more destination IP addresses, it may, at 812, extractproperties, for example port numbers and protocol type, of any relevantuplink packets and optionally perform packet analysis, using for exampledeep packet inspection (DPI) techniques. At 814, the local P-GW 314/414may invoke a bearer mapping function on any resultant data, which may besource and/or destination IP address(es), source and/or destination portnumber(s), protocol type packet properties, and optionally DPI andstatistical analysis. Based on the resultant bearer mapping function andmapping rules, resultant data may be forwarded/routed onto a relevantdestination bearer/GRE tunnel established for a target UE served by thelocal system/RAN. At 816, the local P-GW 314/414 may provide an input toa routing/forwarding/re-encapsulation routine, for example destinationbearer/GRE tunnel ID, which may determine whether the packet should bekept. If, at 810, the P-GW 314/414 determines that no contextinformation has been found, it may discard the packet, in some casessilently, and transition to 816. At 818, the packet classification andmapping stage may stop and transition to 718 from FIG. 7 and notterminate packets.

Referring to FIG. 9, a flow diagram 900 illustrating example operationsof a wireless communications system is shown in accordance with anexample of the invention. In this example, the flow diagram 900 mayillustrate an emergency user plane operation at a local P-GW, forexample local P-GW 312/412. Initially, at 902, the emergency user planeoperation commences and, at 904, local P-GW 312/412 may be operable todetect an encapsulated tunnelled packet, which may be a user planepacket. At 906, the local P-GW 312/412 may extract a tunnel end pointID, identifier, from a tunnel header pre-pended to the detected packetand, at 908, search local context information. The local P-GW 312/412may search an internal database to determine whether context informationexists for the detected packet using a search key, for example searchkey tunnel endpoint identifier (TEid) for GTP tunnels, However, othertunnelling protocols, such as GRE, may use applicable tunnel identifiers(e.g. GRE key). If the local P-GW 312/412 determines that contextinformation does not exist for the detected packet, it may discard thepacket 910, in some examples silently and stop the procedure at 912.

If, however, the local P-GW 312/412 determines that context informationdoes exist for the detected packet, it may, at 914, determine whether ornot an emergency operation is necessary. In this example, an emergencyoperation may be required if there is no detected backhaul linkavailable between local P-GW 312/412 and a higher level system, forexample EPC 304. If, at 914, the local P-GW 312/412 determines that anemergency operation is required, it may, at 916, extract a number ofproperties from the detected packet such as, for example, IP packetdestination IP address(es), port numbers, and properties that may bedetermined by DPI, before transitioning to 918 and invoking a bearermapping function. If the local P-GW 312/412 determines 914 that anemergency operation is not required, it may determine whetherre-encapsulation 920 is required. In this example, local P-GW 312/412may also invoke this step, 920, after invoking a bearer mapping functionin 918. If local P-GW 312/412 determines that re-encapsulation 920 isrequired, it may change at 924 the current tunnel that may be a GTPtunnel, to a GRE tunnel, or vice versa, before transitioning to 926 andmodifying a search key, for example TEid, in the GRE or GTP tunnelheader. If the local P-GW 312/412 determines that re-encapsulation, 920,is not required, it may also transition to 926 and modify a search key,for example TEid, in the GRE or GTP tunnel header before forwarding thedetected packet onto its destination at 928.

So far, discussion of some illustrated embodiments has focussed onaspects such as managing and routing packets between, for example, amain P-GW and a local P-GW via at least one tunnel. Further, some otherexample embodiments have focussed on aspects of switching of a localP-GW, for example if a backhaul link, tunnel, may no longer be availablebetween a main P-GW in an EPC and a local P-GW in an access network. Forcompleteness, techniques are also envisaged of how to handlebearer(s)/PDN connection(s) management procedures in examples where abackhaul link is available and subsequently unavailable. Further, someprevious examples have discussed routing packets and switching for UEsalready attached to the network. In some examples, new UEs may need toattach to the network when there is no backhaul link available.

Referring to FIG. 10, a flow diagram 1000 illustrating an example ofbearer and PDN connection management for a wireless communicationssystem is shown in accordance with an example of the invention.Initially, at 1002, the procedure begins, and the system determineswhether an incoming packet is one of a dedicated bearer establishmentrequest for an already established PDN connection 1004, a new PDNconnection establishment request for an already attached UE 1006, or anattach request for a new UE 1008. At 1010, irrespective of thedetermination, a local P-GW, for example local P-GW 312/412 maydetermine whether a main P-GW is available, for example main P-GW 306.If the local P-GW 312/412 determines that main P-GW 306 is available, itmay begin forwarding messages to the main P-GW 306, analyse content ofthe messages and based on any information gathered, local UE contextinformation may be created/updated/deleted. Bearer management proceduresrequire UE context information to be updated or deleted, and the PDNconnection management procedures require UE context information to becreated/updated/deleted.

In some examples, the local P-GW 312/412 may act as a proxy P-GW thatbuilds up UE context information based on signalling messages exchangedbetween main P-GW 306 and S-GW, for example S-GW 314/414, via the localP-GW 312/412. Although the local P-GW 312/412 may terminate the S5bearer, the local P-GW 312/412 may appear to the S-GW 314/414 as themain P-GW 306, and appear to the main P-GW 306 as the S-GW 314/414.Therefore, the main P-GW 306 may be unaware of the local P-GW 312/412,which may have polymorphic functions depending on which network entityuses its services. Specifically, at 1012, the local P-GW 312/412 maycreate context information and establish a proxy mode of operation(one-to-one bearer binding/packet forwarding between itself and mainP-GW 306). At 1014, the local P-GW 312/412 may forward signalling to themain P-GW 306 and, at 1016, context information at the main P-GW 306 maybe created. At 1018, the main P-GW 306 may be operable to allocate IPaddresses in the case of 1006 and 1008 as a backhaul link may beavailable.

If local P-GW 312/412 determines that main P-GW 306 is not available at1010, for example there is no backhaul link available, the local P-GW312/412 may be operable to terminate any control plane signalling anddefer any communication with the main P-GW 306 until the main P-GW 306is reachable and/or operational again. This signalling may be requiredto allow the main P-GW 306 to obtain current UE context information,i.e. to be synchronised with UE context information stored at the localP-GW 312/412. Specifically, at 1020, the local P-GW 312/412 may beoperable to allocate IP addresses in the cases of 1006 and 1008. Itshould be noted that there is no IP routing within the local system asall data is carried over tunnels, for example GTP tunnels 322. IPaddress allocation at 1020 may only be required to meet applicationlayer requirements at UEs, and to enable packet forwarding onto GTP-Utunnels in the local P-GW 312/412. However, issues may arise as how tomanage IP address allocation, and how to manage the local P-GW 312/412if the main P-GW 306 becomes available again.

In this example, from an IP layer viewpoint, UE terminals may beconsidered as ‘always ON’. In this example IP address(es) assigned foran existing PDN connection 1004 may not be changed, as this may disturbthe application layer. However, in some examples, it may be possible toupdate IP address(es) for existing PDN connections 1004 if DHCP isutilised. In the case of 1006 and 1008 where the main P-GW 306 is notavailable, the local P-GW 312/412 may be required to defer anyregistration/signalling with main P-GW 306 until it is reachable again.In the case of UEs, the local P-GW 312/412 may be required to providesufficient information to the UEs in order to enable establishment of anew PDN connection 1006, for example to provide/assist in IP addressallocation. If IP address(es) are allocated at the time a PDN connectionis established, it may also be required to utilise an IP address thatcan be routable at the main P-GW 306 or external PDN, as otherwise theIP address may need to be re-assigned when the main P-GW 306 isreachable again. In the case of 1006 and 1008, there may be severalexamples of how IP address(es) may be allocated, for example:

-   -   IPv6 stateless configuration;    -   IPv6 state full configuration (i.e. via dynamic host        configuration protocol (DHCP) v6);    -   via any point-to-point (PPP) like protocol;    -   IPv4 state full configuration (DHCP);    -   IPv4 via control plane signalling (at the time a UE may attach        1008 or a new PDN connection may be established 1006).

Referring to IPv6 stateless configuration, due to a large IPv6 addressspace available, allocation utilising this configuration should bepossible, provided that the IPv6 prefix used by UEs is topologicallycorrect with the main P-GW 306. However, the local P-GW 312/412 may berequired to trigger deferred signalling exchange when the main P-GW 306becomes reachable again. In this case, GTP-C protocol messages may beutilised if GTP tunnelling is used, or MIP/PMIP signalling if not.

Referring to IPv6 state full configuration, the local P-GW 312/412 maybe required to trigger deferred signalling exchange as defined for IPv6stateless configuration. However, IP addresses assigned to UEs may needto be topologically correct with the main P-GW 306 and signalled by thelocal P-GW 312/412 to the main P-GW 306 when deferred signalling istriggered, unless UEs have triggered DHCP rebinding, which may result inallocation of a different IP address. If the assigned IP address(es) isnot topologically correct, it may need to be rebound by the DHCP serverto make it topologically correct. This is not desirable for theapplication layer.

Referring to any PPP like protocol, if the assigned IP address is nottopologically correct with the main P-GW 306, the IP address may need tobe reassigned. For PPP protocols, the network control protocol (NCP)protocol is generally used for network layer configuration. If the NCPprotocol cannot reassign the IP address, the PPP client may be requiredto re “dial-in”, which may not be optimal as UEs should not be aware ofthe availability problems of main P-GW 306.

Referring to IPv4 state full configuration, similar principles apply asdefined in relation to IPv6 state full configuration.

Referring to IPv4 via control plane signalling, the UEs IP addresses maybe assigned by an HSS within the core network, in which case it can betopologically correct with the main P-GW 306. Otherwise, UEs may berequired to reattach to the network, which can be disruptive for theapplication layer.

Referring to a further example, an IP address allocation scheme isdescribed that may allow local P-GW 312/412 to allocate IP addressesthat may be topologically correct with the main P-GW 306, while the mainP-GW 306 may not be reachable. In this example, local P-GWs may have asmall pool of IP addresses set aside that are topologically correct withthe local P-GW 312/412 to handle occasions where a new PDN connection1006 is required while there is no current connection with the main P-GW306. Such an arrangement may allow for seamless operation when localP-GW 312/412 becomes available.

In some examples, if it is not possible to allocate addresses that aretopologically correct with the main P-GW 306, the local P-GW may performNAT, or similar, if IP addresses are not topologically correct (PMIPtunnelling could be used, in which case NAT would be located at localP-GW).

In another example, there may be several main P-GWs (406) in the system.In this case, there may be less freedom in determining IP addresses ofP-GW selection functions and IP address allocation, as otherwise IPaddress allocation for UEs establishing a PDN connection while there isno backhaul link may need to re-establish PDN connections when the mainP-GW becomes available.

At 1022, the local P-GW 312/412 may activate local packet detection androuting/forwarding procedures for new bearers/PDN connections. At 1024,the local P-GW 312/412 may repeatedly check for availability of mainP-GW 306. In this case, the local P-GW 312/412 may continue to checkavailability of the main P-GW until the main P-GW 306 becomes available.Once the local P-GW 312/412 has determined that the main P-GW isavailable, it may, at 1026, trigger deferred signalling with the mainP-GW 306, and forward any pending signalling to the main P-GW 306. At1028, the local P-GW 312/412 may create context information at the mainP-GW 306 and, at 1030, the main P-GW 306 may perform IP addressvalidation and optionally reassignment if required for 1006 and 1008. At1032, the local P-GW 312/412 may be operable to then stop local packetdetection and routing/forwarding for all bearers/PDN connections, andapply one-to-one mapping for all packets received on the bearers.

In some examples, at least two P-GWs may be allocated for each PDNnetwork. This may provide, advantageously, the ability for the PDNnetwork to communicate with UEs while a backhaul link is available.Further, aspects of the invention may, advantageously, allowcommunication with UEs while a backhaul link is not available, withoutthe need to re-establish bearers or perform a new registration with thenetwork. Aspects of the invention may further facilitate seamlessswitching between a mode of operation where there is not a backhaul linkand a mode of operation where there is a backhaul link. In this case,there may be no need to re-allocate IP addresses to UEs when there is aswitching transition between these two modes. In this way, during anoutage scenario, for example where there is no longer a backhaul link,packets for which destinations are known may be forwarded to therelevant UEs, and packets for which destinations are not known may bediscarded.

Referring now to FIG. 11, there is illustrated a typical computingsystem 1100 that may be employed to implement software controlledswitching between a first mode of operation where a backhaul link may beavailable and a second mode of operation where a backhaul link may notbe available in some example embodiments of the invention. Computingsystems of this type may be used in wireless communication units. Thoseskilled in the relevant art will also recognize how to implement theinvention using other computer systems or architectures. Computingsystem 1100 may represent, for example, a desktop, laptop or notebookcomputer, hand-held computing device (PDA, cell phone, palmtop, etc.),mainframe, server, client, or any other type of special or generalpurpose computing device as may be desirable or appropriate for a givenapplication or environment. Computing system 1100 can include one ormore processors, such as a processor 1104. Processor 1104 can beimplemented using a general or special-purpose processing engine suchas, for example, a microprocessor, microcontroller or other controllogic. In this example, processor 1104 is connected to a bus 1102 orother communications medium.

Computing system 1100 can also include a main memory 1108, such asrandom access memory (RAM) or other dynamic memory, for storinginformation and instructions to be executed by processor 1104. Mainmemory 1108 also may be used for storing temporary variables or otherintermediate information during execution of instructions to be executedby processor 1104. Computing system 1100 may likewise include a readonly memory (ROM) or other static storage device coupled to bus 1102 forstoring static information and instructions for processor 1104.

The computing system 1100 may also include information storage system1110, which may include, for example, a media drive 1112 and a removablestorage interface 1120. The media drive 1112 may include a drive orother mechanism to support fixed or removable storage media, such as ahard disk drive, a floppy disk drive, a magnetic tape drive, an opticaldisk drive, a compact disc (CD) or digital video drive (DVD) read orwrite drive (R or RW), or other removable or fixed media drive. Storagemedia 1118 may include, for example, a hard disk, floppy disk, magnetictape, optical disk, CD or DVD, or other fixed or removable medium thatis read by and written to by media drive 1112. As these examplesillustrate, the storage media 1318 may include a computer-readablestorage medium having particular computer software or data storedtherein.

In alternative embodiments, information storage system 1110 may includeother similar components for allowing computer programs or otherinstructions or data to be loaded into computing system 1100. Suchcomponents may include, for example, a removable storage unit 1122 andan interface 1120, such as a program cartridge and cartridge interface,a removable memory (for example, a flash memory or other removablememory module) and memory slot, and other removable storage units 1122and interfaces 1120 that allow software and data to be transferred fromthe removable storage unit 1118 to computing system 1100.

Computing system 1100 can also include a communications interface 1124.Communications interface 1124 can be used to allow software and data tobe transferred between computing system 1100 and external devices.Examples of communications interface 1124 can include a modem, a networkinterface (such as an Ethernet or other NIC card), a communications port(such as for example, a universal serial bus (USB) port), a PCMCIA slotand card, etc. Software and data transferred via communicationsinterface 1124 are in the form of signals which can be electronic,electromagnetic, and optical or other signals capable of being receivedby communications interface 1124. These signals are provided tocommunications interface 1124 via a channel 1128. This channel 1128 maycarry signals and may be implemented using a wireless medium, wire orcable, fiber optics, or other communications medium. Some examples of achannel include a phone line, a cellular phone link, an RF link, anetwork interface, a local or wide area network, and othercommunications channels.

In this document, the terms ‘computer program product’,‘computer-readable medium’ and the like may be used generally to referto media such as, for example, memory 1108, storage device 1118, orstorage unit 1122. These and other forms of computer-readable media maystore one or more instructions for use by processor 1104, to cause theprocessor to perform specified operations. Such instructions, generallyreferred to as ‘computer program code’ (which may be grouped in the formof computer programs or other groupings), when executed, enable thecomputing system 1100 to perform functions of embodiments of the presentinvention. Note that the code may directly cause the processor toperform specified operations, be compiled to do so, and/or be combinedwith other software, hardware, and/or firmware elements (e.g., librariesfor performing standard functions) to do so.

In an embodiment where the elements are implemented using software, thesoftware may be stored in a computer-readable medium and loaded intocomputing system 1100 using, for example, removable storage drive 1122,drive 1112 or communications interface 1124. The control logic (in thisexample, software instructions or computer program code), when executedby the processor 1104, causes the processor 1104 to perform thefunctions of the invention as described herein.

In one example, a tangible non-transitory computer program productcomprises executable program code operable for, switching between afirst mode of operation where a backhaul link may be available and asecond mode of operation where a backhaul link may not be available insome example embodiments of the invention.

It will be further appreciated that, for clarity purposes, the describedembodiments of the invention with reference to different functionalunits and processors may be modified or re-configured with any suitabledistribution of functionality between different functional units orprocessors is possible, without detracting from the invention. Forexample, functionality illustrated to be performed by separateprocessors or controllers may be performed by the same processor orcontroller. Hence, references to specific functional units are only tobe seen as references to suitable means for providing the describedfunctionality, rather than indicative of a strict logical or physicalstructure or organization.

Aspects of the invention may be implemented in any suitable formincluding hardware, software, firmware or any combination of these. Theinvention may optionally be implemented, at least partly, as computersoftware running on one or more data processors and/or digital signalprocessors. For example, the software may reside on non-transitorycomputer program product comprising executable program code to increasecoverage in a wireless communication system.

In one example, the program code may be employed by a packet datanetwork gateway (P-GW) located in a second network, for supporting userplane data in a wireless communications system that additionallycomprises a first network having a first packet data network gateway(P-GW). The executable program code may be operable for, when executedat the packet data network gateway (P-GW), monitoring and buildingterminal device context information for a plurality of terminal devicesbeing served with user plane data by a backhaul link of the secondnetwork; determining an operational status of at least one of: thebackhaul link, first P-GW, and in response to the processor determiningthat at least one of: the backhaul link, first P-GW, is unavailable,performing at least one of: terminating signalling between the firstnetwork and at least one of: a mobility management entity (MME), and/orSGW; deferring signalling between the first network and at least one ofthe MME and/or the SGW; performing at least some functionality of thefirst P-GW.

In one example, the program code may be employed by a packet datanetwork gateway (P-GW) located in a second network, for supporting userplane data in a wireless communications system that additionallycomprises a first network having a first packet data network gateway(P-GW). The executable program code may be operable for, when executedat the packet data network gateway (P-GW), monitoring data supplied overthe backhaul link to or from the first network; determining anoperational status of at least one of: the backhaul link, first P-GW,and in response to determining that both of the backhaul link and firstP-GW, are available; performing at least one of: allowing access betweenthe first P-GW and the terminal device; triggering differed signallingbetween the base station and the first network; and returning to a statethat monitors data supplied by the backhaul link from the first networkto determine an operational status of at least one of: the backhaullink, first P-GW.

Thus, the elements and components of an embodiment of the invention maybe physically, functionally and logically implemented in any suitableway. Indeed, the functionality may be implemented in a single unit, in aplurality of units or as part of other functional units.

Those skilled in the art will recognize that the functional blocksand/or logic elements herein described may be implemented in anintegrated circuit for incorporation into one or more of thecommunication units. For example, the integrated circuit may be suitablefor a (second) packet data network gateway, P-GW, located in a (second)network for supporting control plane data in a wireless communicationssystem that additionally comprises a (first) network having a first P-GWoperably couplable to the P-GW, and a serving gateway, S-GW. Theintegrated circuit comprises a processor arranged to: monitor and buildterminal device context information for a plurality of terminal devicesbeing served with user plane data by a backhaul link of the secondnetwork; and determine an operational status of at least one of: thebackhaul link, first P-GW. In response to the processor determining thatat least one of: the backhaul link, first P-GW, is unavailable, theprocessor is arranged to perform at least one of: terminate signallingbetween the first network and at least one of a mobility managemententity (MME), the S-GW; defer signalling between the first network andat least one of the MME, the S-GW; perform at least some functionalityof the (first) P-GW.

Furthermore, it is intended that boundaries between logic blocks aremerely illustrative and that alternative embodiments may merge logicblocks or circuit elements or impose an alternate composition offunctionality upon various logic blocks or circuit elements. It isfurther intended that the architectures depicted herein are merelyexemplary, and that in fact many other architectures can be implementedthat achieve the same functionality.

Although the present invention has been described in connection withsome example embodiments, it is not intended to be limited to thespecific form set forth herein. Rather, the scope of the presentinvention is limited only by the accompanying claims. Additionally,although a feature may appear to be described in connection withparticular embodiments, one skilled in the art would recognize thatvarious features of the described embodiments may be combined inaccordance with the invention. In the claims, the term ‘comprising’ doesnot exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means,elements or method steps may be implemented by, for example, a singleunit or processor. Additionally, although individual features may beincluded in different claims, these may possibly be advantageouslycombined, and the inclusion in different claims does not imply that acombination of features is not feasible and/or advantageous. Also, theinclusion of a feature in one category of claims does not imply alimitation to this category, but rather indicates that the feature isequally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply anyspecific order in which the features must be performed and in particularthe order of individual steps in a method claim does not imply that thesteps must be performed in this order. Rather, the steps may beperformed in any suitable order. In addition, singular references do notexclude a plurality. Thus, references to ‘a’, ‘an’, ‘first’, ‘second’,etc. do not preclude a plurality.

I claim:
 1. A packet data network gateway, P-GW, located in a secondnetwork for supporting control plane data in a wireless communicationssystem that additionally comprises a first network having a first P-GWoperably couplable to the P-GW, and a serving gateway, S-GW; the P-GWcomprising a processor arranged to: monitor and build terminal devicecontext information for a plurality of terminal devices being servedwith user plane data by a backhaul link of the second network; anddetermine an operational status of at least one of: the backhaul link,the first P-GW, wherein, in response to the processor determining thatat least one of: the backhaul link, the first P-GW, is unavailable, theprocessor is arranged to perform at least one of: terminate signallingbetween the first network and at least one of: a mobility managemententity (MME), the S-GW; defer signalling between the first network andat least one of: the MME, the S-GW; perform at least one functionalityof the first P-GW.
 2. The packet data network gateway of claim 1 whereinthe processor is arranged to build the terminal device contextinformation from signalling used to establish a single packet datanetwork connection.
 3. The packet data network gateway of claim 2wherein the processor is operably coupled to a memory element arrangedto store the terminal device context information.
 4. The packet datanetwork gateway of claim 2 wherein the processor is further arranged toextract signalling information between the first P-GW and at least oneof the MME, the S-GW and perform at least one of: adapt the extractedsignalling information passed between at least one of the MME, the S-GWand the first P-GW; and forward the extracted signalling information tothe first P-GW.
 5. The packet data network gateway of claim 1 where theprocessor is arranged to monitor and build the terminal device contextinformation for the plurality of terminal devices being served with userplane data by the second network.
 6. The packet data network gateway ofclaim 5 wherein the processor is further arranged to check a destinationaddress of received packets to determine whether the received packetsare destined for any of the plurality of terminal devices, and extractone or more properties of said received packets if they are destined forany of the terminal devices served with user plane data by the secondnetwork.
 7. The packet data network gateway of claim 6 wherein theprocessor is arranged to further perform packet analysis or statisticalanalysis on said received packets.
 8. The packet data network gateway ofclaim 5 wherein the processor is further arranged to check a destinationaddress of received packets to determine whether the received packetsare destined for any of the plurality of terminal devices, and discardsaid received packets if they are not destined for any of the terminaldevices served with user plane data by the second network.
 9. The packetdata network gateway of claim 5 wherein the processor is furtherarranged to check a destination address of received packets to determinewhether the received packets are destined for a local packet datanetwork, and discard said received packets if they are not destined forthe local packet data network.
 10. The packet data network gateway ofclaim 6 wherein the processor is arranged to further invoke a bearermapping function within the second network.
 11. The packet data networkgateway of claim 8 wherein the processor is arranged to further invokethe bearer mapping function within the second network based on at leastone from a group of: one or more source IP address(es), one or moredestination IP address(es), one or more source port number(s), one ormore destination port number(s), one or more protocol type packetproperties, packet analysis performed on said received packets.
 12. Thepacket data network gateway of claim 1 wherein the processor beingarranged to perform at least some functionality of the first P-GWcomprises the processor being arranged to allocate an Internet protocoladdress to the terminal device from the plurality of terminal devicesupon receipt of a message from the terminal device indicating arequirement to attach or establish a new packet data network, PDN,connection.
 13. A method of operation of a packet data network gateway,P-GW, located in a second network for supporting control plane data in awireless communications system that additionally comprises a firstnetwork having a first packet data network gateway, P-GW, operablycouplable to the P-GW and a serving gateway, S-GW; the methodcomprising, at the P-GW: monitoring and building terminal device contextinformation for a plurality of terminal devices being served with userplane data by a backhaul link of the second network; determining anoperational status of at least one of: the backhaul link, the firstP-GW, and in response to the processor determining that at least one of:the backhaul link, the first P-GW, is unavailable, performing at leastone of: terminating signalling between the first network and at leastone of: a mobility management entity, MME, the S-GW; deferringsignalling between the first network and at least one of the MME, theS-GW; performing at least some one functionality of the first P-GW. 14.The method of claim 13 further comprising building the terminal devicecontext information from signalling used to establish a single packetdata network connection.
 15. The method of claim 13 further comprisingstoring the terminal device context information.
 16. The method of claim13 further comprising extracting signalling information between thefirst P-GW and at least one of the MME, the S-GW and performing at leastone of: adapting the extracted signalling information passed between atleast one of the MME, the S-GW and the first P-GW; forwarding theextracted signalling information to the first P-GW.
 17. The method ofclaim 13 further comprising monitoring and building the terminal devicecontext information for the plurality of terminal devices being servedwith user plane data by the second network.
 18. The method of claim 17further comprising checking a destination address of received packets todetermine whether the received packets are destined for any of theplurality of terminal devices, and extracting one or more properties ofsaid received packets if they are destined for any of the terminaldevices served with user plane data by the second network.
 19. Anon-transitory computer program product comprising executable programcode for operation of a packet data network gateway, P-GW, located in asecond network for supporting control plane data in a wirelesscommunications system that additionally comprises a first network havinga first P-GW and a serving gateway, S-GW, the executable program codeoperable for, when executed at the P-GW: monitoring and buildingterminal device context information for a plurality of terminal devicesbeing served with user plane data by a backhaul link of the secondnetwork; determining an operational status of at least one of: thebackhaul link, the first P-GW, and in response to the processordetermining that at least one of: the backhaul link, the first P-GW, isunavailable, performing at least one of: terminating signalling betweenthe first network and at least one of: a mobility management entity,MME, the S-GW; deferring signalling between the first network and atleast one of the MME, the S-GW; performing at least some onefunctionality of the first P-GW.
 20. An integrated circuit for a packetdata network gateway, P-GW, located in a second network for supportingcontrol plane data in a wireless communications system that additionallycomprises a first network having a first P-GW operably couplable to theP-GW, and a serving gateway, S-GW; the integrated circuit comprising aprocessor arranged to: monitor and build terminal device contextinformation for a plurality of terminal devices being served with userplane data by a backhaul link of the second network; and determine anoperational status of at least one of: the backhaul link, the firstP-GW, wherein, in response to the processor determining that at leastone of: the backhaul link, the first P-GW, is unavailable, the processoris arranged to perform at least one of: terminate signalling between thefirst network and at least one of a mobility management entity (MME),the S-GW; defer signalling between the first network and at least one ofthe MME, the S-GW; perform at least one functionality of the first P-GW.